Kristin Cavallari. [Photo/Agencies]

Kristin Cavallari is furious that the sex of her baby has been revealed by her partner's teammate.

The 25-year-old star and Jay Cutler are expecting their first baby and today (02.05.12), Jay's Chicago Bears teammate Earl Bennett announced on 'The Boers and Bernstein Show' radio show that they are having a boy, leaving Kristin fuming.

A source told Hollyscoop.com: "They are not happy that something so personal was revealed on a radio show, especially Jay - he didn't want anyone to know what they were having."

Speaking on the radio show, football player Eric said: "New toys, a baby on the way--he's having a boy-and, you know, I'm excited for Jay. It's a great time."

Afterwards, the show's hosts revealed his blunder, declaring: "Jay's having a boy. I don't think anybody knew that before then."

Kristin has previously revealed she couldn't wait to find out if she was having a boy or girl, but would not mind what it turns out to be.

She said: "I do want to find out what I'm having, I couldn't wait. I don't care what the sex is. A little girl would be fun, to put little tutus on her, but a boy would be great, so I don't care."